In my 2d FDTD code, I use a Gaussian pulse (in time) to excite Electric field at a point (center) in 2D space (only air) as a soft source. During simulation, Ez spreads out isotropically as an impulse (symmetric about z axis), Hx and Hy spread out like a dipole radiation (one of the two patterns are symmetric about x axis and the other about y axis).
I have read about monopole, dipole and so on sources which may be excited at a point but unable to find exact functions they use there. What does my simulation actually represent? Is it a monopole, dipole or what? If its a dipole then how to calculate its dipole moment from simulation data or parameters?
The statement " Ez spreads out isotropically as an impulse (symmetric about z axis)" appears to be self-contradictory!
Isotropic and symmetric about a given axis at the same time?
I used the word 'isotropic' because Ez spreads out from the point of excitation exactly the same way in all directions on the x-y plane and that is symmetric about the z axis!
This is the simplest of sources so it actually represents many things. It can be used to simulate fluorescence or quantum dot sources. In combination with other dipole sources, it could represent an antenna source. Since it creates a cylindrical wave, you can use it to approximate the radiation from other antennas as well. It is also just a simple way to inject electromagnetic waves into a simulation. You can use it to test reflections at your boundaries or to excite periodic structures for band diagrams.
Take a look at the following Lecture series, including YouTube recordings:
http://emlab.utep.edu/ee5390fdtd.htm
For some discussion on dipole sources, take a look at Lectures 11 and 19. The YouTube videos include some useful animations.
Hope this helps!
Thanks Prof. Raymond for your response, I learnt FDTD only from your higly effective youtube lecture series and I recommend everyone reading this post to check them out because they are probably the best lectures on the entire INTERNET to start using FDTD in minimum time.
But Prof. Raymond, My question is- should I call that a dipole source or a monopole source? If its a dipole then how to calculate its dipole moment from simulation data or parameters.
An antique and very informative video from Canadian Airforce (link given) related to point sources and connection with dipole
https://www.youtube.com/watch?v=7bDyA5t1ldU
- Badges
- Science topic